Apparatus for pulverizing materials



April 23, 1946. L. F. BEACH 2,398,774

APPARATUS FOR PULVERIZING MATERIALS Filed April 8, 1942 4 Sheets-Sheet l ATTORNEY April 23, 1946.

F. BEACH 2,398,774

v APPARATUS FOR PULVERIZING MATERIALS Filed April 8, 1942 4 Sheets-Sheet 24 INVENTOR u on/A 554a Z24 ATTOR EY A ril 23, 1946. F. BEACH 2,393,774

APPARATUS FOR PULVERIZING MATERIALS Filed April 8, 1942 4 Sheets-Sheet s 1 H UN I l I I i T Ea lNVENTOR 04255546 ATTORNEY A ril 23, 1946. I L. F. BEACH APPARATUS FOR PULVERIZING MATERIALS Filed April 8, 1942 4 Sheets-$11691; 4

Patented Apr. 23, 1946- UNITED STATES PATENT OFFICE 2.398.774 APPARATUS FOR PULVERIZING MATERIALS Ludiow F. Beach, Charleston, 8. 0., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application April 8, 1942, Serial No. 438,132

16 Claims.

the mill, to maintain the quantity or volume of the charge in the mill substantially constant irrespective of the output demand on the pulverizer. Should the amount of charge in the mill exceed a predetermined normal level, the charge may spill over into one or more of the mill trunnions and may restrict the air passage by which air enters the mill and the connection through which the pulverized product leaves the mill resulting in a decrease in the output of the pulverizer. Should the charge in the mill fall below a predetermined normal level there would be a deficiency of charge in the mill which will result in excessive wear of the grinding balls and liners of the mill.

In accordance with the present invention, ma-

, terial to be pulverized is continuously and uninterruptedly fed to the mill but the amount fed is automatically controlled to maintain a constant or substantially constant supply of material in the mill irrespective of the output demands on the pulverizer. By maintaining a substantially constant quantity of material in the mill, a substantially constant state of agitation is maintained. in consequence of which a substantially constant concentration of pulverized material in suspension in the air in the mill per unit quantity of the air is maintained and a constant output of a product of the desired fineness is secured.

The nature and advantages of the invention Fig. 6 is a wiring diagram of the apparatus of the present invention.

. Like characters of reference refer to like parts throughout the several views.

'Rei'erring to the drawings, reference numeral ill designates the steel shell of the drum of a ball mill for pulverizing coal or other material. The drum or shell is provided with trunnions II on opposite ends thereof which are rotatably mounted in bearing supports I2. A ring gear I3 is suitably secured to the drum l0 and is driven by a motor H through a shaft l5 and a pinion it. The shaft 15 is rotatably mounted in bearings l1 and I8. Material to be pulverized is fed to the drum Ill through a feed pipe It in communication with a chute 20. The chute 28 is connected to the trunnion l I through which the material passes into the drum. Air for the mill is introduced through an opening 2! in the side of the chute 20, the size of which opening may be varied by adjusting the slide 22. Pulverized material is withdrawn from the drum through the trunnion at the opposite end of the drum, not shown, by the suction of an exhauster fan, the degree of suction depending upon the position of the damper 22.

.A disc-type coal feeder 23, comprising a rotatable feed table 24 housed within a casing 25, has a chute 26 positioned adjacent the periphery of the table 24 at one side of the casing 25. The

table 24 is keyed to a shaft 26 having a worm wheel 21 enmeshed with a, worm 28 on a shaft 28 which is driven by a motor 30. The surface of the feed plate has a plurality of corrugations I thereon formed by a plurality of spaced, raised ribs 3| which are curved from adjacent the center of the plate toward the periphery, the spaces will be understood from the following description taken in coniunction with the accompanying drawings forming a part thereof, and in which:

Fig. 1 is a view in elevation, with parts thereof broken away, of a ball mill pulverizer together with the charge controlling apparatus embodying the invention;

Fig. 2 is an enlarged view of the charge controlling apparatus taken on the line 22 of Fig. 3, part of the apparatus being shown in transverse section and part being shown in elevation;

Fig. 3 is a plan view of a portion of the charge controlling apparatus shown in Fig. 1;

Fig. 4 is a Plan view taken on the line 4-4 of Fig. 5 is a side view, partly in section and partly in elevation. taken on the line 5-5 of Fig. 4, and

between the ribs gradually increasing toward the periphery. The spaces between the ribs are adapted to receive fine particles of coal and through the action of centrifugal force, the par-- ticles are moved toward the periphery of the plate.

A hopper 32, which receives coal from a bunker in the usual manner, is adapted to discharge the coal onto the rotating feed table 2i at the central portion thereof, and the coal is moved to the outer periphery of the table by centrifugal force. Coal is adapted to be swept from the feed table 24 while it is rotating by an arcuate shaped shear arm 33 secured to a shear plate 34. The shear plate is secured to a vertically extending shaft 35 which is pivotally mounted in the casing 25 adjacent the chute 28' and extends through the top ofthe casing. Pivotal movement is imparted to the shaft it by an arm 36 secured at one end increase the area of the table swept by the sheararm and thereby increase" the amount of coal swept into the chute 28', or by turning the shaft 85 to move the plate 88 away from the central portion of the feed table 24 todecrease the area of the table swept by the shear arm and thereby decrease the amount of coal swept into the chute 28.

Mechanism for actuating the shear arm 88 to control the amount of coal swept from the feed table 24 comprises a reversing motor 88 having a shaft 88 connected through a coupling 48 to the' driven or high speed shaft 4| of a speed reducer 42. The drive or low speed shaft 48 of the speed reducer is adapted to rotate at a substantially lesser speed than the driven shaft 4|. of the shaft 48 extends through the casing 44 in which the actuating mechanism is mounted, and has secured thereto an arm 45 on which is pivotally mounted an'actuating rod 48 which is connected to the actuating rod 81 by means of a universal joint 41. The shaft 48 extends outwardly or the opposite side of the speed reducer One end and has a contact plate 48 of an electrical nonconductive material secured thereto and adapted to rotate therewith. A three-step pulley 48 is mounted on the shaft 48 outwardly of the contact plate 48 so as to be free to rotate on the shaft. ,A contact arm 58 having a contact 5| thereon, is secured to the pulley and is adapted to cooperate with contacts 52 and 58 positioned on the plate 48. A spring 54 is fastened at one end to the pulley 48 and at the opposite end is secured to the plate 48 by means of spring tensionadjusting screw 55. The spring 54 is so positioned that when the spring is under ten-.

sion, a clockwise force is exerted on the pulley 48. An actuating line 58 is secured to the pulley 48 at 51' and extends downwardly over the side of the pulley opposite the side on which the spring 54 is positioned. The line 58 is adapted to exert a force acting in a counterclockwise direction on the pulley 48 against the tension or the spring 54.

The line 58 is actuated by a controller 51 which comprises a casing 58 in which-is located a bell float 58, the lower edg or which is submerged in a liquid, such as water or mercury. The edge of the bell float may be provided on the inside thereof with a bank 88 of cork or other material to aid in floating the bell. The bell has a substantially vertical rod 8| secured thereto and which moves with the bell. The rod 8| extends beyond the top and the bottom of the casing 58. The, bottom of the rod 8| is attached to a spring 62, the

tension of which is'ad'apted to exert a downward force on the rod. The spring 82 is anchored to may be positioned on the top of the controller inbell 58 is in communication with the interior of the drum through a level control tube 58. The drum end or the tube 88 projects downwardly into the drum Hi to a point slightly below the normal level desired to be maintained in the drum.

It is desirable to limit the extent to which the shear arm 88 may be moved toward the central portion of the feed table 24 and also to limit the extent to which the shear arm may be moved away from the central portion of the feed plate. Limit switches 18 and 1| are employed for this purpose. The limit switch I8 as shown diagrammatically in Fig. 3, comprises a movable contact I2 which is normally held in engagement with fixed contacts I8 and I4 by spring I2 which are in circuit with the motor 88, as will hereinafter be fully described. The movable. contact 18 has an actuating arm I5 thereon which is adapted to be actuated by the arm 45 on the shaft 48. When the shear arm88 reaches the extent of its movement inward toward the center of the feed table, that is, when the shear arm 88 extends entirely across the feed table 24, the arm 45 which actuates the shear arm through the actuating rods 81 and 48, as will hereinafter be fully described, engages the movable contact arm I5 and breaks th circuit to the motor 88 and thereby prevents further movement of the shear arm toward the center of the feed table. The limit switch H which is similar in construction and in operation to the switch I8, is also adapted to be actuated by the arm 45. When the shear arm 88 reaches the extent of its movement away from the'center of the feed table, for example, when the shear arm extends over only a minor portion of the table, the arm 45 engages the movable contact arm I8 on the switch II and breaks the circuit to the motor 88 preventing further movement of the shear arm away from the center of the feed table.

An auxiliary limit switch I1, Fig. 2, which is adapted to be tripped by a tripping plate 18 on the rod 8| of the controller 51, is mounted on the top of the controller and enclosed by a cover 18. This switch is adapted to act in the event of failure of the limit switch I8 and serves the same purpose. The switch I1 is a mercury switch comprising a glass tube 18 secured to a mounting block I8 pivoted to a support 80. As shown, the mounting block 18 is tilted by the tripping plate I8 as it moves upwardly with the bell float 58. The mass of mercury is thereby caused to move away from the switch point 8| thus breaking the contact between the points 8| and 82, thereby interrupting the circuit to the motor 88 and preventing further clockwise rotation of the shaft 48 and contact plate 48 which prevents further movement of the shear arm 88 away from the center of the feed table, since further actuation of rods 81 and 48 by movement of the arm 45 in aclockwise direction by the shaft 481s prevented. A counter-weight 88 is positioned on the mounting block I8 and is'adapted to return the switch II to its closed position when the position or the plat I8 permits. A similar auxiliary limit switch such manner that it will be tripp d by the tripping plate 18 when it moves downwardly to a predetermined point against the tension of the spring 54.

The movement of hell 58 is responsive to the differential in pressure between the chamber 8'! within the bell and the chamber 85 in which the bellis positioned, and this diii'erential will vary with changes in level of thematerial being pulverisedinthemlll. Since thedrumendofthe reference tube 88 is permanently beyond contact with the charge, the pressure in chamber 88 will be the pressure in the mill. Covering and uncovering of the drum end of the level control tube 88 by coal, as hereinbeiore mentioned, renders the tube more or less eifective to conduct air, and the greater the extent to which the end is covered by an increasing charge of material in the drum, the less eifective the tube 88 is rendered in conducting the air. The pressure in the tube 88 and therefore in the chamber 81, approaches atmospheric pressure as the drum end of the control tube 88 is covered by the charge in the drum, As the level oi. the charge iii the drum I8 rises above the desired level, and the drum end of the level control tube 68 becomes covered, the pressure in the tube and in chamber 81 rises while the pressure in tube 88 and chamber 88 remains substantially the same, with the result that the bell 88 rises and moves the rod 8| upwardly. The tension in the sprin 84 causes the pulley 48 to move in a clockwise direction on the shaft 43 as viewed in Fig. 2, without moving the shaft, thereby causing the arm 88 and contact 8i to move toward the contact 83. The extent to which the pulley 48 is turned in a clockwise direction by tension of the spring 84 is governed by the extent to which the drum end 68 of the control tube 68 is covered by the material in the mill. The more the end 88 is covered by the material, the nearer the pressure in the tube 68 and chamber 81 of the control 81 approaches atmospheric pressure, the more the bell 88 and the rod 8| and line 88 move upwardly, and the more the spring 84 imparts movement of the pulley 48 in a clockwise direction as seen in Fig. 2. When the level of the material in the drum rises to a point slightly higher than the desired'level, the drum end of the tube 88 is obstructed to such an extent as to cause the pressure in the tube 68 to rise and thereby cause upward movement of the bell 88, rod 8| and line 88, sufficient to allow the contact i to be brought into engagement with the contact 83, by reason of the action of the spring 84 on the pulley 48.

As shown in the wiring diagram of Fig. 6, which illustrates one manner in which the control mechanism may be connected, the contact 8| is in electrical connection with one pole of an electrical source S through the line 88, single pole double throw switch 81, and double pole single throw switch 88. The other pole of the source S is in electrical connection with one terminal of the reversing motor 38 through the switch 88 through the lines 88 and 88. Therefore, when relay 88 are normally closed. The otherend of the coil 88 is connected to the line 82 which has current flowing therethrough from the other pole of the electrical source. The coil 88 is thereby energized, causing the contacts I88 and m oi the relay 88 which are normally open, to be brought into engagement, thereby causing the contacts I82 and I83 of said relay which are normally closed. to become disengaged. Engagement of the contacts I88 and IM permits current to flow from the line I84 which is connected to the electrical conduit 88, through these contacts and into the line I88, whence the current passes into one end of the coil I88 of the relay I81 which receives current from line 82. The coil I88 is thereby energized, causing the contacts I88 and I88 of the relay I81, which are normally open, to be brought into engagement. Current passes from the contact I88 into one end oi. the coil II8 of the relay I I l, the other end of the coil receiving current from the line 82. The coil H8 is thus energized, causing the contacts II2 and H3 which are normally open, to be brought into engagement. Engagement of the contacts H2 and H3 permits current to flow from the line I84 into the line H4 and thence into the switch I I8 which is closed when the automatic feed control is functioning. From the switch II8 the current passes into the line II8, through the limit switches 1i and 11 and into the terminal II1 of the motor 38. Therefore, when the contacts 8! and 83 are in engagement, current from one pole of the electrical source flows from the switch 88 through the contacts 83 and 84 of the switch 81, through the lines 88 and I84, contacts H2 and H3 of the relay III, thence into the motor through the switch II8, line II6, limit switches 1| and 11, and motor terminal I I1. Current from the opposite pole of the source passes from the switch 88 into the line 88 and 88 directly to a motor 38.

Connecting the motor 38 into the circuit as described, causes the motor to turn the shaft 38 and high speed shaft H of the speed reducer 42 in such a direction that the low speed shaft 43 of the speed reducer is turned in a clockwise direction as viewed in Fig. 2. Turning of the shaft 43 in this direction, causes the arm 48 to move in a clockwise direction which in turn causes rods 48 and 31 to move to the right as shown in Fig. 4,

which causes the arm 38 on the pivot shaft 38 to the switch 88 is closed, electrical current passes from one pole of the electrical source S, through the switch 88, line 88 and line 88, to the motor 38. The line 88 is also connected to one terminal of a switch 8| which when closed, connects the lines 88 and 82 so that current from one pole of the source may flow into the line 82. When the switch 81 is closed so that the movable contact 83 engages the fixed contact 84, current flows from the opposite pole of the source through the switch 88, switch 81, line 88 and into the contact 8|. When the contact 8i engages the contact 83, current flows from the contact 8| into the contact 83, thence into the line 83' and the contact 84' o! the relay 88. From the contact 84', current flows into the contact 88 of the relay 85 thence through the line 81 into one end of the coil 88 of the relay 88. The contacts 84' and 88 of the turn in a counterclockwise direction thereby moving the shear plate 34 and the shear arm 33 in a counterclockwise direction, or away from the center of the feed table 24, thereby causing a lesser portion of the feed table to be covered by the arm and causing less coal to be fed into chute 28' and thence into the drum I8.

Turningof the shaft 43 in a clockwise direction as viewed in Fig. 2. by the motor 33, also causes the contact plate 48 to turn in a clockwise direction. The tension of the spring 84 will cause the contact 8| to follow the contact 83, thereby holding said contacts in engagement as'the contact 83 rotates with the plate 48, since the spring tends to exert a clockwise rotative force on the pulley 48 to which the arm 88 is attached. The

beyond this point, thereby breaking the engagement between these contacts. Disengagement of the contacts 3i and 33 prevents further passage of current through the line 33. contact points 34 and 93 ;of the relay 95 and line 31 into the coil 9301 the relay, thereby causing the coil to become deenergized and permitting the contacts I33 and II to return to their normally open position which prevents passage of current into the line I35 and into the coil I33 of the relay I31. Coil I03 is deenergized and the contacts I93 and Ill are permitted to return to their-normally open position. With the disengagement oi the contacts I03 and I39, current no longer flows into the relay III from the relay I01, which deenergizes the coil II 3 of said relay and permits the contact III to move out of engagement with the contact H3.

Breaking of the engagement between the contacts H2 and H3 prevents current from flowing into the motor through the terminal II I by way or the line II4, switch II5, line H9 and limit switch II. Accordinglyzthe motor 39 is stopped and further counterclockwise movement (Fig. 4) of the shear arm 33 is prevented. The extent to which the shear arm 33 may move in this counterclockwise direction,.is limited by the limit switch II which is adapted to be engaged by the arm 35 so that the flow of current through the line II3 to the motor terminal I I! is broken, and the motor is stopped. The contacts of the limit switch are adapted to be disengaged when the shear arm 33 extends over only a minor portion of the surface of the feed table 24 adjacent the outer periphery thereof. The auxiliary limit switch 11 is actuated by the tripping plate 19 in the event the limit switch II fails to operate.

Should the level of the charge in the mill decrease, thereby reducing the extent to which the drum end of the level control tube 93 is covered, the suction in the tube 39 will be increased and will cause the bell 59 to move downwardly, thereby moving the rod BI and line 55 downwardly and imparting a counterclockwise movement (Fig. 2) to the pulley 49 against the tension of the spring 54. counterclockwise movement of the pulley moves the arm 50 and contact 5| in a counterclockwise direction, the contact 5I moving toward the contact 52'on the plate 49. The extent to which the pulley 49 is turned in a counterclockwise direction is governed by the extent to which the bell 59 is moved downwardly by the suction in the chamber 61 and tube 59. As the level of the charge in the drum It falls toward the drum end of the tube 59, the suction in the tube increases until the bell 59 has been moved downwardly to an extent suflicient to 'move the contact 5| into engagement with the contact 52.

When the contact GI engages the contact 52, the switches 81, 88 and 9| being closed, electrical current flows from one pole of the source S through the line 96 into the contact 5| thence into the contact 52, whence it passes through the line I20, the normally closed contacts I02 and I03 into the line I2I, and thence into the coil I22 and energizing the coil I22, since the opposite end of the coil is in communication with the opposite pole of the source S through the lines I24 and 92, switch 9I, line 89 and switch 99. Energization of the coil I22 causes the normally open contacts I25 and I2Ii to engage and to permit current to flow through contacts I25 and I25 from the lines 85, I04 and I21, into the line I28. Current in the line I28 flows into one end of the coil I29 of the relay I30, theopposlte end of which is connected to the line 92 by the line I3I. The coil I29 thereby is energized and the normally open contacts I32 and I33 are closed. Current from the line I04 asesme -pasees through the contacts In and us into the line I34; thence to one end of the coil I33 of the relay I33 thereby energizing the coil, since the opposite end thereof is connected to the line 32 by means of the lead I31. Energizing the coil I33 causes the normally open contacts I33 and I33 to close and permits current to flow from the line I34 through the line I43, through the closed contacts I33 and I39 into the line I, thence through the switch III which is closed. into the line I42, through the limit switch 10 to the terminal I43 0! the motor 39 which is caused to turn in a direction opposite to the direction to which it turns whn current flows into the motor through the terminal I ll, Turning 01' the motor in the opposite direction, causes the low speed shaft 430! the speed reducer to be turned in a counterclockwise direction (Fig. 2) which turns the arm 45 in a counterclockwise direction moving the rods 45 and 31 to the left and causing the arm 39, shaft 33,

- shear plate 34, and shear arm 33, to move in a clockwise direction. The shear arm 33 thereby is caused to move toward the central portion of the feed table 24 and to-cover a greater extent of the surface of the feed table and to cause a greater amount of material to be passed into the chute 23 and into the drum I0.

counterclockwise rotation (Fig. 2) of the shaft 43 by the motor 39 also causes the contact plate 49 to turn in a counterclockwise"direction. The downward pull exerted on the rod 3! and line 53 .will cause the contact 5| to follow the contact 52 and to hold these contacts in engagement as the contact 52 rotates with the plate 49. The counterclockwise rotation of thecontact 5I and the pulley 49 is against the tension of the spring 54, thereby increasing this tensions The contacts 5| and 52 remain in engagement until the pulley 49 reaches a point in its counterclockwise rotation where the tension of the spring 54 equals the downward force exerted by the bell 59. When this state of equilibrium is reached, counterclockwise movement of the pulley 49 and contact 5I ceases. The motor 38 will move the plate 49 and contact 52 slightly beyond this point, thereby breaking the engagement between the contacts 5I and 52. Disengagement of the contacts H and 52 prevents iurther'passage of current through the line I20. contact points I02 and I03 of the relay 99, and line I2I into the coil I22 of relay I23, which causes the coil to become deenergized prevents further passage of current through the line I, switch II5, line I42 and limit switch I0 into the motor '39 through the terminal I43. The motor 39 is thereby stopped and further clockwise movement (Fig. 4) of the shear arm 33 is prevented. The extent to which the shear arm 33 may rotate in a, clockwise direction is limited by the limit switch 1.0 which is engaged by the arm 45 so-that the flow of current through the line i I 42 to the motor terminal I43 is broken and the motor 38 is stopped. Thecontacts of the limit switch are adapted to be disengaged when the shear arm 33 extends entirely across the surface of the feed table 24 from the outer to the inner periphery thereof. An auxiliary limit switch, such as the switch 11, may be used in the line I42 which would be engaged by the tripping plate I8 in its downward movement to tilt the switch and break the connection between the contact points therein in a manner similar to breaking of the connections between the contacts in the switch 11.

It is desirable at certain times, particularly during the starting of the pulveriz'er, to operate the shear arm 33 independently of the automatic control hereinbefore described. For this purpose, as shown in Fig. 6, hand operated push buttons I45 and I45 are provided. When it is desired to control the operation of the motor 33 and thereby to actuate the shear arm 33 by means of the push buttons I45 and I43, the switch 88 is closed, the switches 9i and are opened, and the movable arm 93 of the switch 81 is turned so that the contact thereon engages the fixed contact I41 which is connected to one fixed contact I48 of the switch I48 and one fixed contact I49 of the switch I43 through the lines I50 and lil. The other fixed contact I52 of the push button switch I45, is connected to the line I42 by means of the electrical conduit I53, while the second fixed contact I54 of the push button switch I48 is connected to the line I I6 by means of the lead I55.

The switch I45 is closed when it is desired to move the shear arm 33. in a clockwise direction (Fig. 4) toward the inner periphery of the feed table 24. Current will then flow from one pole of the source S through the switch 88 into the contacts 93 and I41 of the switch 81, thence through the lines I SI and I50 into the contact I48 of the switch I45. The current then flows through the movable contact of this switch into the fixed contact I52, whence it flows into the lines I53 and I42 through the limit switch I0, thence into the motor 38 through the terminal I43, and causes the motor to turn in a direction to rotate the shaft 43 of the speed reducer in a counterclockwise direction (Fig. 2). When it is desired to turn the shaft 43 in a clockwise direction and thereby turn the shear arm in a counterclockwise direction and toward the outer periphery of the feed table 24, the switch I45 is closed and the switch I45 is opened. Current will then flow from the line I50 into the fixed contacts I49 and I54 of the switch I46 thence through lines I55, H8 and limit switches II and I1 into terminal I" of the motor 38, causing the motor to operate.

With the apparatus or this invention the quantity of the charge in the drum of the mill is automatically maintained at a predetermined level irrespective of the output demand on the pulverizer. mill may vary in accordance with the output demand on the mill, the material to be pulverized is continuously fed to the mill. The means for feeding material to the drum i adapted to be stopped when the mill is stopped. This may be accomplished by any desirable means cooperating with the feed motor 30 which will interrupt the flow of current to said motor when the mill motor I4 is stopped, for example by connecting the lead wires 84 and 85' of the switches 84 and 85 respectively to a switch connected to an electrical source so that when the switch S connected to the source is opened the flow or current to the motor I4 and 30 is interrupted.

Since variations may be made in the form of the invention herein disclosed, it will be understood that the invention is not to be limited except by the scope of the appended claims.

While the amount fed to the drum of the What is claimed is:

1. Pulverizing apparatus comprising an airswept revoluble drum adapted to contain a body of material, a feeding plate adapted to receive material on a surface thereof and from which surface material is supplied to the drum, a motor for constantly rotatingsaid feeding plate while said pulverizing apparatus is in operation, a feeding member pivoted adjacent the feeding plate to turn on an axis substantially parallel to the axis of rotation of said plate, said feeding member cooperating with the surface of the plate, actuating means for turning the feeding member in a clockwise or a counter-clockwise direction on the pivot in relation to the plate for controlling the amount of material removed from the plate including a reversible electric motor, and control means for said motor comprising a switch for changing the direction of operation of said motor, aid switch having a contact plate actuated by the reversible motor, spaced contacts on the plate, a movable contact adapted to be moved into engagement with one of the first-mentioned contacts to operate the motor in one direction and into engagement with the other of said firstmentioned contacts to operate the motor in the opposite direction and a control member for moving and holding said movable contact in engagement with said first-mentioned contacts, said member comprising means operated by the difference in pressure betweenmembers conducting separate, relatively small quantities of air from points within the drum, one of aid points being disposed below the maximum desired level of material therein and another of said points being disposed above said maximum desired level, said engagement between the movable contact and the first-mentioned contacts being broken when the level rises above or falls below said predetermined level.

2. In pulverizing apparatus having a drum adapted to contain material to be pulverized. means for pulverizing the material therein, means for feeding to the drum material to be pulverized including electrically actuated means for changing the quantity of material fed to the drum, and means movable .in response to variations in the quantity of material in the drum, control means for said electrically actuated means comprising a first electrical contact movable upon movement of said electrically actuated means, and a second electrical contact arranged for engagement and disengagement with the first contact and movable with said movable means, said contacts being in circuit with said electrically actuated means, the arrangement being such that the operation of said electrically actuated means is controlled to change the quantity of material fed to the drum.

3. In pulverizing apparatus having a drum adapted to contain material to be pulverized, means for pulverizing the material therein, means for feeding to the drum material to be pulverized including electrically actuated means for varying the uantity of material fed to the drum, and means movable in response to variations in the quantity of material in the drum, control means for said electrically actuated means comprising a plurality of electrical contacts movable upon movement of said electrically actuated means, and another electrical contact arranged for engagement and disengagement with said plurality of contacts and movable with said movable means, said contacts being in circuit with said electrically actuated means, the arrangement being such that the electrically actuated means is for feeding to the drum material to b pulverized including electrically actuated means for varyin the quantity of material fed to the drum, and means movable in response to variations in the quantity of material in the drum, control means for said electrically actuated means comprising spaced electrical contacts movable upon movement of the electrically operated means, and another electrical contact disposed between the spaced contacts and arranged for engagement and disenga ement therewith, said other contact being movable with said movable means, said contacts being in circuit with said electrically actuated means, the arrangement being such that the electrically actuated means is operated to increase the amount of material fed to the drum when said other contact is in engagement with one of the spaced contacts, and is operated to decrease the amount of material led to the drum when said other contact is in engagement with the other spaced contact thereby to vary the amount of material fed to the drum to maintain a constant quantity of material therein.

5. In pulverizing apparatus having a drum adapted to contain materialto be pulverized, means for pulverizing the material therein, means for feeding to the drum material to be pulverized including electrically actuated means for varying the quantity oi material fed to the drum, and means movable in response to variation in the quantity of material in the drum, control means for said electrically actuated means comprising contact mounting means movable upon movement or said electrically actuated means, spaced contacts disposed on the mounting means, another electrical contact disposed between the spaced contacts and mounted for movement independently of the contact mounting means, said other contact normally being disengaged from the spaced contacts and arranged for engagement therewith and movable with said movable means. and-resilient means normally under tension connected to said othercontact and to the contact mounting'means so that movement of the other contact with said movable means toward one of the spaced contacts will be against the tension of said resilient means and movement oi said other contact toward another spaced contact will be with the tension oi said resilient means, said contacts being in circuit with the electrically operated means, the arrangement being such that when the movable means responds to a decrease or the quantity oi material in the mill the other electrical contact is moved into engagement with one of the spaced contacts to cause the electrically operated means to be operated to increase the amount of material fed to the drum. and when the movable means responds to an increase in the quantity of material in the drum the other electr cal contact is moved into engagement with another of the spaced contact to cause the elec trically operated means to be operated to decrease the amount of material fed to the mill.

8. In pulverizing apparatus having a drum adapted to contain material to be pulverized, means for pulverizing the material therein, means for feeding to the drum material to be Dulveriud including electrically actuated means for varying the quantity of material fed to the drum, and means movable in response to variations in the quantity of material in the drum, control means for said electrically actuated mean comprising contact mounting means movable upon movement of th electrically actuated means, spaced contacts on the mounting means, another electrical contact between the spaced contacts arranged for engagement therewith and mounted for movement independently of the contact mounting means, means operatively connecting the other contact with the movable means, and a spring normally under tension connected to said other contact and to the contact mounting means so that movement of the other contact into engagement with one of the spaced contacts by the movable means will be against the tension of the spring and movement of the other contact into engagement with another of the spaced contacts will be with the tension of the spring, said contacts being in circuit with the electrically operated means so that engagement of the other contact with one of the spaced contacts will cause actuation of the electrically-actuated means to increase the quantity oi material red to the drum and engagement of the other contact with another of the spaced contact will cause actuation of the electrically actuated means to decrease the quantity of material fed to the drum, the arrangement being such that the spaced contacts are moved out of engagement with the other contact by movement of the contact mounting means by the electrically actuated means, when the amount of tension of the spring determined by the position of the movable means is insumcient to hold the other contact and the spaced contacts in engagement.

7. In pulverizing apparatus having a drum adapted to contain material to be pulverized, means for pulverizing the material therein, means for feeding to the drum material to be pulverized including electrically actuated means for changin: the quantity of material fed to the drum, and means movable in response to variations in'the quantity of material in the drum, control means for said electrically actuated means comprising a first electrical contact movable upon movement of said electrically actuated means, and a second electrical contact arranged for engagement and disengagement with the first contact, said contacts being in circuit with the electrically actuated, means, the second contact having movement with the movable means, theinterval of engagement between the first and second contacts being determined by the extent of movement of the movabl means, the arrangement being such that the operation of said electrically operated memher is controlled to change the quantity of matemeans for changing the quantity of material fed to the drum, and means movable in response to the nressure'in a member conducting a relatively small quantity. of air from' a point within the drum'disposed below the maximum desired level of material therein, control means for said elecassume trically actuated means comprising a first electrical contact movable upon movement of 'said electrically actuated means, and a second electrical contact arranged for engagement and disengagement with the first contact, said contacts being in circuit with the electrically operated member, the second contact having movement with the movable means, the interval of engagement between the first and second contacts being determined by the extent of movement of the movable means, the arrangement being such that the operation of said electrically operated member is controlled to change the quantity of material fed to the drum.

9. In pulverizing apparatus having an airswept drum adapted to contain material to be pulverized, means for pulverizing the material therein, means for feeding to the drum material to be pulverized including electrically actuated means for changing the quantity of material fed to the drum, and means movable by the difference in pressure between members conducting separate, relatively small quantities of air from points in the drum, one of said points being disposed below the maximum desired level of material therein and another of said points disposed above said maximum desired level, control means for said electricall actuated means comprising a first electrical contact movable upon movement of said electrically actuated means, and a second electrical contact arranged for engagement and disengagement with the first contact. said contacts being in circuit with the electrically operated member, the second contact having movement with the movable means, the interval of engagement between the first and second contactsrbeing determined by the extent of movement of'the movable means, the arrangement being such that the operation of said electrically operated mem-' ber is controlled to change the quantity of material fed to the drum.

10. In pulverizing apparatu having a drum adapted to contain material to be pulverized, means for pulverizing the material therein, means for feeding to the drum material to be pul-' verized including a feeding plate adapted to receive material on a surface thereof, an electrically operated adjustable member cooperating with said plate for changing the amount of material fed therefrom to the drum, and means movable in response to variations in the quantity of material in the drum, control means for said electrically operated adjustable member comprising a first electrical contact movab e upon operation of the adjustable member, and a second electrical contact arranged for engagement and disengagement with the first contact and movable with said movable means, said contacts being in circuit with said electrically operated member, the arrangement being such that the operation of said electrically operated member is controlled to change the quantity of material fed to the drum,

11. In pulverizing apparatus having a drum adapted to contain material to be pulverized, means for pulverizing the material therein,

.means for feeding to the drum material to b pulverized including a feeding plate adapted to receive material on a surface thereof, an adjustable member cooperating with said plate for controlling the amount of material fed therefrom to the drum, a reversible electrical motor for operating the adjustable member to increase and decrease the amount of material fed to the drum, and means movable in response to variations in the quantity of material in the drum, control means for controlling the operation of the electrical motor comprising a plurality of electric contacts movable by operation of said motor, and another electrical contact arranged for engagement and disengagement with said plurality of contacts and movable with said movable means, said contacts being connected in circuit with the electrical motor so that upon engagement of one of the plurality of contact by said other contact the reversible motor will operate the electrically operated member to increase the amount of material fed to the drum and upon engagement of another of the plurality of contacts the reversible motor will operate the electrically operated member to decrease the amount of material fed to the drum, the arrangement being such that the operation of said electrically operated member is controlled to vary the quantity of material fed to the drum to'maintain a substantially constant quantity of material therein.

12, In pulverizing apparatus having a drum adapted tocontain material to be pulverized, means for pulverizing the material therein, means for feeding to the drum material to be pulverized including a feeding plate adapted to receive material on a surface thereof, an adjustable member cooperating with said plate for controlling the amount of material fed therefrom to the drum, electrical driving means for operating the adjustable member to increase and decrease the amount of material fed to the drum, and means movable in response to variations in the quantity of material in the drum, control means for controlling the operation of the electrical driving means comprising a plurality of electric contacts movable by operation of said driving mean, and another electrical contact arranged for engagement and disengagement with said plurality of contacts, said contacts being connected in circuit with the electrical driving means, said other electrical contact having movement with the movable means, the interval of engagement between said other contact and one of said plurality of contacts being determined by the extent of movement of the movable means, the arrangement being such that the operation of said electrically operated member is controlled to vary the quantity of material fed to the drum to maintain a substantially constant quantity of material therein.

13. In pulverizing apparatus having a drum adapted to contain material to be pulverized, means for pulverizing the material therein, means for feeding to the drum material to be pulverized including a feeding plate adapted to receive material on a surface thereof, an adjustable member cooperating with said plate for controlling the amount of material fed therefrom to the drum, a reversible electric motor for operating the adjustable member, and means movable in response to variations in the quantity of material in the drum in respect to a predetermined quantity therein, control means for controlling the operation of the electrical motor comprising contact mounting means movable in opposite directions by operation of said motor, spaced contacts disposed on the mounting means, another electrical contact disposed between the spaced contacts and mounted for movement independently of the contact mounting means, the contacts being in electrical circuit with the motor, means operatively connecting said other electric contact with the movable means, whereby movement of the movable means in response to variations of the quantity of material in the drum in respect to a predetermined quantity will cause the other contact to engage one of the spaced contacts when the quantity of material falls below a predetermined amount to operate the motor and the adjustable member to feed a greater amount of material to the drum and cause said other contact to engage the other spaced contact when the quantity of material increases beyond a predetermined amount to thereby operate the motor and the adjustable member to feed a lesser amount of material to the drum, the interval of operation of said motor in either direction by the engagement of said other contact with the spaced contacts being determined by the amount of movement imparted to the other contact by the movable means.

14. In pulverizing apparatus having a drum adapted to contain material to be pulverized, means for pulverizing the material therein, means for feeding to the drum material to be pulverized including a feeding plate adapted to receive material on a surface thereof, an adjustable member cooperating with said plate for controlling the amount of material fed therefrom to the drum, a reversible electric motor for operating the adjustable member, and means movable in response to variations in the level of material in the drum in respect to a predetermined level therein, control means for controlling the operation of the electrical motor comprising contact mountingmeans mounted on a shaft to turn therewith, the shaft being rotated by said motor, spaced contacts disposed on the mounting means, another electrical contact disposed between thespaced contacts and mounted for movement independently of the contact mounting means, the contacts being in electrical circuit with the motor, means operatively connecting said other electric contact with the movable means whereby movement of the movable means in response to variations of the level of the material in the drum will cause the other contact to engage one of the spaced contacts when the level of the material falls below a predetermined level to operate the motor and the adjustable member to feed of material fed therefrom to the drum, electrical driving means for operating the adjustable mem ber to increase and decrease the amount of material fed to the drum and means movable in response to the pressure in a member conducting a relatively small quantity of air from a point within the drum disposed below the maximum desired level of material therein, control means for controlling the operation of the electrical driving means comprising a plurality of electric contacts movable by operation of said driving means, and another electrical contact arranged for engagement and disengagement with said plurality of contacts, said contacts being in circuit with the electrical driving means, said other electrical contact having movement with the movable means, the interval of engagement between said other contact and one of said plurality of contacts being determined by the extent of movement of the movable means, the arrangement being such that the operation of said electrically operated member is controlled to vary the quantity of material fed to the drum to maintain a substantially constant level of material therein.

16. In pulverizing apparatus having an airswept revoluble drum adapted to contain a body of material, a feeding plate adapted to receive material on a surface thereof and from which surface material is supplied to the drum, a motor for constantly rotating said feeding plate while said pulverizing apparatus is in operation, a feeding member pivoted adjacent the feedin plate to turn on an axis substantially parallel to the axis of rotation of said plate, said feeding member cooperating with the surface or the plate, control means for turning the feeding member in a clockwise or a counter-clockwise direction on the pivot in relation to the plate for controlling the amount of material removed from the plate including a reversible electric motor, and control means for said last-mentioned motor comprising a switch for changing the direction of operation of said motor, said switch having a contact plate actuated by the reversible a greater amount of material to the drum and cause said other contact to engage the other spaced contact when the level of the material increases beyond a predetermined level to thereby operate the motor and the adjustable member to feed a lesser amount of material to thedrum, the interval of operation of said motorin either direction by the engagement of said other contact with the spaced contacts being determined by the amount of movement imparted to the other contact by the movable means.

15. In pulverizing apparatus having an airswept drum adapted to contain material to be pulverized, means for pulverizing the material therein, means for feeding to the drum material to bev pulverized including a feeding plate adapted to receive material on a surface thereof, an electrically operated adjustable member cooperating with said plate for controlling the amount motor, spaced contacts on the plate, a movable contact adapted to be moved into engagement with one of the first-mentioned contacts to operate the motor in 'one direction and into engagement with the other of said first-mentioned contacts to operate the motor in the opposite direction, and a control member for moving and holding said movable Contact in engagement with said first-mentioned contacts, said member comprising means operated by the difference in pressure between members conducting separate, relatively small quantities of air from points within the drum, one of said points being disposed below the maximum desired level of material therein and another of said points being disposed above said maximum desired level, said engagement between the movable contact and the first-mentioned contacts being broken when the level rises above or falls below said predetermined level.

LUDLOW F. BEACH. 

